fix: added extraction of byte-images in excel (#804)

* fix(msexcel): ignore Mypy checking for _find_images_in_sheet function

Signed-off-by: Jiun An Tsai <andrew@247365-Macbook.local>

* fixed some issues

Signed-off-by: Peter Staar <taa@zurich.ibm.com>

* reformatted the code

Signed-off-by: Peter Staar <taa@zurich.ibm.com>

* pinned pillow in pyproject

Signed-off-by: Peter Staar <taa@zurich.ibm.com>

---------

Signed-off-by: Jiun An Tsai <andrew@247365-Macbook.local>
Signed-off-by: Peter Staar <taa@zurich.ibm.com>
Signed-off-by: Michele Dolfi <dol@zurich.ibm.com>
Co-authored-by: Jiun An Tsai <andrew@247365-Macbook.local>
Co-authored-by: Michele Dolfi <dol@zurich.ibm.com>

tests/data/groundtruth/docling_v2/test-01.xlsx.itxt

@@ -7,4 +7,5 @@ item-0 at level 0: unspecified: group _root_
     item-6 at level 2: table with [5x3]
   item-7 at level 1: section: group sheet: Sheet3
     item-8 at level 2: table with [7x3]
-    item-9 at level 2: table with [7x3]
+    item-9 at level 2: table with [7x3]
+    item-10 at level 2: picture

tests/data/groundtruth/docling_v2/test-01.xlsx.md

@@ -48,4 +48,6 @@
 | 3           | 4            | 5            |
 | 3           | 6            | 7            |
 | 8           | 9            | 9            |
-| 10          | 9            | 9            |
+| 10          | 9            | 9            |
+
+<!-- image -->